Batch dishwashers are dishwashers which can be manually loaded and unloaded. Batch dishwashers (also called “box-type warewashers”) may be hood-type dishwashers (“hood-type warewashers”) or front-loader dishwashers (“front-loader warewashers”). Front-loader dishwashers may be under-counter machines, top-counter machines or free-standing front-loader dishwashers.
A dishwasher which is in the form of a batch dishwasher usually has a treatment chamber for cleaning washware. The treatment chamber generally has arranged beneath it a wash tank in which liquid from the treatment chamber can flow back due to the force of gravity. The wash tank contains wash liquid which is usually water to which detergent may be added if required.
A dishwasher which is in the form of a batch dishwasher also has a wash system with a wash pump, a line system which is connected to the wash pump, and with a large number of spray nozzles which are formed in the at least one wash arm. The wash liquid contained in the wash tank can be conveyed from the wash pump to the spray nozzles via the line system and be sprayed onto the washware to be cleaned through the spray nozzles in the treatment chamber. The sprayed wash liquid then flows back into the wash tank.
Conveyor dishwashers (“conveyor warewashers”) are, in particular, flight-type dishwashers (“flight-type warewashers”) or rack-conveyor dishwashers (“rack-conveyor warewashers”). Conveyor dishwashers are usually used in the commercial field. In contrast to batch dishwashers, in which the washware to be cleaned remains stationary in the machine during the cleaning process, the washware is transported through various treatment zones of the conveyor dishwasher in the case of conveyor dishwashers.
A conveyor dishwasher usually has at least one prewash zone and at least one main-wash zone which is arranged downstream of the prewash zone or zones as seen in the transportation direction of the washware. As seen in the transportation direction, at least one postwash zone and at least one final-rinse zone, which is downstream of the postwash zone, are generally arranged downstream of the main-wash zone or zones. As seen in the transportation direction, the washware, which is either accommodated directly on a conveyor belt or is retained by racks, usually runs, in the transportation direction, through an inlet tunnel, the following prewash zone or zones, main-wash zone or zones, postwash zone or zones, final-rinse zone or zones and a drying zone, into an outlet section.
The abovementioned wash zones of the conveyor dishwasher each have an associated wash system which has a wash pump and a line system which is connected to the wash pump, via which wash liquid is supplied to the spray nozzles of the wash zone. The wash liquid which is supplied to the spray nozzles is sprayed onto the washware, which is transported through the respective wash zones by a transportation apparatus of the conveyor dishwasher, in the respective wash zone. Each wash zone has an associated wash tank in which sprayed liquid is accommodated and/or in which wash liquid for the spray nozzles of the relevant zones is provided.
In the case of the conveyor dishwashers which are usually known from the prior art, final-rinse liquid in the form of fresh water, which may be pure or mixed with further additives, for example rinse aid, is sprayed onto the washware via the spray nozzles of the final-rinse zone. At least some of the final-rinse liquid sprayed is transported from zone to zone, counter to the transportation direction of the washware, via a cascade system.
The sprayed final-rinse liquid is collected in a tank (postwash tank) of the postwash zone, from which it is conveyed to the spray nozzles (postwash nozzles) of the postwash zone via the wash pump of the wash system which is part of the postwash zone. In the postwash zone, wash liquid is rinsed off from the washware. The liquid which accumulates in the process flows into the wash tank of the at least one main-wash zone which is arranged upstream of the postwash zone as seen in the transportation direction of the washware. Here, the liquid is usually provided with a detergent and is sprayed onto the washware by a pump system (wash pump), which is part of the wash system of the main-wash zone, via the nozzles (wash nozzles) of the main-wash zone. If no further main-wash zones are provided, the liquid then flows from the wash tank of the main-wash zone into the prewash tank of the prewash zone. The liquid in the prewash tank is sprayed onto the washware via a pump system, which is part of the wash system of the prewash zone, via the prewash nozzle of the prewash zone in order to remove coarse dirt from the washware.
Irrespective of whether the dishwasher is in the form of a batch dishwasher or in the form of a conveyor dishwasher, the dishwashers under consideration here and, in particular, designed for commercial use therefore usually comprise a wash system which has a wash pump which ensures a virtually constant water circulation rate for the duration of a wash process in the treatment chamber (in the case of batch dishwashers) or in the respective treatment zone (in the case of conveyor dishwashers). The respective wash pumps of the wash systems are switched on and switched off by a control device (machine controller) which is part of the dishwasher in accordance with a selected and predefined execution program. The control device is also used to set further process parameters of the wash process, which process parameters are defined in the selected execution program, by actuating suitable components of the dishwasher. Said process parameters include, for example, the temperature of the wash liquid sprayed during the wash process, the nozzle pressure with which the wash liquid is sprayed onto the washware during the wash process, possibly the quantity of wash liquid sprayed during the wash process per unit time, and the washware contact time, that is to say the period of time over which the washware is subjected to the action of wash liquid.
In addition, at least one final-rinse system is provided in the dishwashers under consideration here in order to spray final-rinse liquid in the treatment chamber during a final-rinse phase in the case of batch dishwashers or in a final-rinse zone in the case of conveyor dishwashers. The process parameters which are to be complied with during the final-rinse process are likewise defined in a selected and predefined execution program and are set during the final-rinse process using the control device by suitable actuation of corresponding actuable components of the dishwasher. These process parameters include, for example, the temperature of the final-rinse liquid sprayed during the final-rinse process, the nozzle pressure with which the final-rinse liquid is sprayed onto the washware during the final-rinse process, possibly the quantity of final-rinse liquid sprayed during the final-rinse process per unit time and the washware contact time, that is to say the period of time over which the washware is subjected to the action of final-rinse liquid.
In contrast to conveyor dishwashers, the two main process steps “wash phase” and “final-rinse phase” are performed laterally in succession, but not physically separately, in one zone (treatment chamber) in the case of batch dishwashers.
To this end, a dishwasher which is in the form of a batch dishwasher is normally equipped with two liquid systems which are independent of one another and which are completely separate from one another. One of these two liquid systems is a wash liquid circuit in which—for the purpose of cleaning the washware—the wash liquid from the abovementioned wash tank beneath the treatment chamber is recirculated. The other liquid system is a final-rinse liquid system which can usually have a water heater (“boiler”) for heating fresh water which is used as final-rinse liquid.
Irrespective of whether the dishwasher is designed in the form of a batch dishwasher or in the form of a conveyor dishwasher, the main task of final rinsing using final-rinse liquid is that of removing the wash liquid (detergent solution) remaining on the washware after the wash phase. Accordingly, the final-rinse liquid used is preferably fresh water to which a rinse aid may be added in a metered fashion.
In the case of batch dishwashers, the final-rinse liquid which flows away, during final rinsing, into the tank which is arranged beneath the treatment chamber is additionally used to regenerate the wash liquid accommodated in the tank since the final-rinse liquid (pure fresh water or fresh water which is mixed with rinse aid) which is sprayed in the treatment chamber during the final-rinse phase flows into the tank which is arranged beneath the treatment chamber due to the force of gravity. Before new final-rinse liquid enters the tank in this way during the final-rinse phase in order to regenerate the wash liquid, the same quantity of wash liquid is pumped out of the tank in the case of batch dishwashers.
In principle, washware has to be treated in a washer, in particular dishwasher, in such a way that the washware is in a hygienically satisfactory state after treatment. This means, in particular, that, after treatment, the surfaces of all the items of washware have to be in a state which prevents adverse health effects when the items of washware are subsequently used. This applies for hospitals and homes for people who are physically compromised, but also for mass catering in canteens, refectories and service areas as well as eating and drinking establishments.
In this connection, a working group with effect for the jurisdiction of the Federal Republic of Germany has been formed for addressing hygiene issues from which the standards DIN 10510 and DIN 10512, amongst others, have been developed. These standards are hygiene guidelines which have to be complied with when commercial dishwashers are used, for example in canteens, refectories and service areas and also eating and drinking establishments, in the territorial region of the Federal Republic of Germany. Said hygiene guidelines (DIN 10510 and 10512) specify, in particular, the hygiene requirements for planning and construction and also the operation of commercial dishwashers in order to define the requirements for hygienic operation of a commercial dishwasher applicable in the territory of the Federal Republic of Germany.
In order to be able to comply with the requirements for hygienic operation of a commercial dishwasher defined in the hygiene guidelines applicable in the Federal Republic of Germany, the spray mechanics, that is to say the way in which the detergent solution (wash liquid and final-rinse liquid) acts on the washware, the required minimum temperatures of the wash liquid and final-rinse liquid and the minimum contact time, for example, are defined in this connection (cf. for example chapter 5.4 “Process requirements” of the standard DIN 10510 applicable on the date of application). For example, the hygiene guideline (standard DIN 10510) which is applicable to conveyor dishwashers prescribes that there must be a minimum temperature of 55° C. in the main-wash zone of the dishwasher in the associated wash tank if there is a sufficient quantity of a disinfection component in the wash liquid. Otherwise, the temperature of the wash liquid has to be at least 60° C. In respect of the final-rinse liquid which is to be sprayed in the final-rinse zone of the conveyor dishwasher, the hygiene guideline specifies a minimum temperature of 80° C.
Under certain circumstances, other requirements for the hygienic operation of a commercial dishwasher may apply in the territory outside the Federal Republic of Germany since there are currently no globally applicable hygiene guidelines. In this connection, reference may be made, for example, to the standard NSF/ANSI3 which is applicable in the jurisdiction of the United States of America. In respect of the hygienic operation of a conveyor dishwasher, this guideline specifies, for example, that there has to be a minimum temperature of 66° C. in the main-wash zone of the dishwasher in the associated wash tank, wherein the final-rinse liquid which is to be sprayed in the final-rinse zone of the conveyor dishwasher has to have a minimum temperature of 82° C. In respect of the hygienically satisfactory operation of batch dishwashers, the version of standard NSF/ANSI3 applicable on the date of application specifies that the liquid (wash liquid or final-rinse liquid) sprayed during the wash phase and during the final-rinse phase each have to have a minimum temperature of 74° C.
Further territorially applicable hygiene guidelines, in which the process parameters which are to be complied with during operation of dishwashers are defined, also exist in addition to the abovementioned hygiene guidelines which are applicable in the Federal Republic of Germany and the United States of America. In this connection, it should be noted that there are currently no uniformly applicable hygiene guidelines. In other words, the process parameters which are each specified in the various territorially applicable hygiene guidelines for ensuring hygienically satisfactory operation of dishwashers sometimes differ considerably.
In order for machine manufacturers to be able to offer and sell their range of products on the worldwide market irrespective of the different territorially applicable requirements for hygienic operation, it is currently customary to design the dishwasher or to program the execution program stored in the control device of the dishwasher such that, in principle, the most stringent requirements for the specified process parameters from amongst all of the hygiene guidelines which are to be taken into consideration are met. This ensures that the requirements for hygienic operation which are specified in all territorially applicable hygiene guidelines are met during operation of the dishwasher.
In other words: in order for a dishwasher, in particular commercial dishwasher, to be able to be used irrespective of the region of use, execution programs are usually stored in the control device of the dishwasher, said execution programs having been created taking into account the strictest worldwide standards in respect of hygienic operation. This ensures that, in principle, the respectively applicable local hygiene guidelines are met during operation of the dishwasher.